As you can see from the video above, the biggest change that we'll make to LR2 is integrating the editor within the game. This will have a few benefits:

Like MMR, you'll be able to test levels directly from the editor. No more jumping from one app to another.

One project - we won't have to maintain two projects that share mostly the same code.

What's done?

Whilst the teaser video doesn't seem complicated, there was quite a few steps involved.

Understand the LR2 formats. 4 years on MMR was a great help with this step.

Create the 3 'Editor' buttons for the menu.

Encode these images back into LR2's native XPK format.

Reduce the button background image by 2 pixels to make room for the extra button so it doesn't look cluttered.

Insert these new images back into UI.PRX

New menu buttons

LR2 uses images for buttons rather than just overlaying text. To get the font to look accurate, I took portions of the other buttons to make the word 'Editor' with the 'E' coming from the 'C' in 'Credits'

Faster this time around

I do expect things to be faster this time around because a huge portion of code will be recycled from MMR.
Excluding the format encoding, what you see in the video took under 20 mins to setup.
Simply tell it where the assets are located and the MMR framework does the rest.

What's next?

Editor

One of the first things to do will be to adjust LR2's UI to fit the screen correctly. MMR had top and bottom thatching so adding it to the sides to remove the pillar boxing when scaling to modern screens was easy. Lode Runner 2 has no such pattern and was designed to fill the screen.
To get around this, I'll need to split the UI into smaller portions (currently a 640x480 image) with a horizontal section that can be repeated to pad out the width.

Support tool

At the moment, the tool to explore, extract and add files to LR2 is the same tool we wrote for MMR but with LR2 specific stuff hacked in. Press play and hope for the best.
This will be re-written over the next few weeks.